Neuronal communication Flashcards
Describe how resting potential is maintained in a neurone ?
- Na/K pump = moves 3 Na + out , 2 K+ in by active transport (requires ATP)
- membrane NOT permeable to Na + ions so they cannot diffuse back in so higher conc of na+ outside
- membrane is permeable to K+ ions so they diffuse back out
so outside of the membrane is more +vely charged than inside of membrane - anions in cytoplasm contribute to -ve charge
what is depolarisation ?
- occurs if threshold potential of -50mV is reached
- voltage-gated Na+ channels open (becomes less -ve)
what is repolarisation ?
- at pd of +40 mV the voltage-gated Na+ channels close
- voltage-gated K+ channels OPEN ( K+ diffuses out so more -ve_
what is hyperpolarisation ?
- p.d becomes more negative than resting potential
Stages of an action potential
- resting potential at -60mV = more -ve inside cell
- stimulus causes Na channel to open, Na+ diffuses into the cell down the electrochemical gradient so inside of cell less -ve
- if the threshold pot (-50mV) is reached then depolarisation occurs
- due to positive feedback, voltage-gated Na channels open + influx of Na +
- at pd of +40mV Na+ channels close and k+ channels open
- k+ ions diffuse out of cell so pd becomes more -ve = repolarisation
- overshoot of k+ out of cell causes cell to be more -ve than resting potential = hyperpolarisation
- k + channel closes, na/k pump reuturn neurone to resting potenital
Explain what happens to the Pacinian corpuscle when it is subjected to pressure
- plasma membrane is flattened
- causes stretch mediated Na+ channels to open
- Na+ ions diffuse in, creating generator potential
- if generator potential reaches threshold it triggers action pot
What is summation + spatial and temporal
summation = effect of neurotransmitters combined
spatial summation = action potential arrives from several diff pre-synaptic neurons
temporal summation = action potential in same pre-synaptic neurone.
Why is the Pacinian corpuscle described as a transducer?
- converts mechanical energy into electrical energy
Suggest why deformation of the plasma membrane of the tip of the neuron causes the membrane to become more
permeable to Na+
.
- inc pressure causes stretch-mediated Na channels to open.
all or nothing law
- if threshold value not reached then action potential is not generated
Suggest an explanation for the fact that action potentials are not generated constantly whilst wearing clothes.
- action potentials not generated because
sodium (ion) channels (remain) open
Outline the roles of synapses in the nervous system (3)
- allows neurons to communicate through cell signalling
- ensure transmission is in 1 direction only
- allows, convergence = impulses from
more than one neuron to be passed to a
single neuron - allows divergence = impulses from a
single neuron to be passed to more than
one neuron
Outline the ways in which the structures of a sensory neurone and a motor neurone are similar (4)
- both have dendrites
axon
cell body with a nucleus
myelin sheath
state 3 differences bet structure of a motor and sensory neurone
m = celll body at end vs s = cell body in middle
m = long axon vs s = short axon
m = no dendron vs s = dendron present
where is the parcinican corpusle located
- under skin
